Sickle cell (SC) disease is a heritable hematological disorder characterized by the presence of hemoglobin S (Hb-S) that has a markedly decreased solubility in a deoxygenated state when compared to that of, for example, hemoglobin A.
Hb-S exists in a homozygous state (S/S) known as sickle cell anemia or in a heterozygous state (A/S) known as sickle cell trait. Homozygous (S/S) individuals commonly exhibit symptoms of severe hemolytic anemia and/or vascular occlusion, which can lead to complications including chronic fatigue; chronic pain; infections; lung, liver and heart injury; leg ulcers; retinopathies; inflammation; arthritis; splenomegaly; and chronic lung infections. While heterozygous (A/S) individuals are normally asymptomatic, they may also develop severe complications, including early end stage renal failure, renal medullary carcinoma, and polycystic kidney diseases.
Sickle Cell disease affects millions of people worldwide, however, Sickle Cell disease is most common in people whose ancestors came from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia. One-third of all indigenous inhabitants of Sub-Saharan Africa carry the Hb-S gene. In the United States, according to the Center for Disease Control and Prevention, about 90,000 to 100,000 people suffer from sickle cell anemia, while about 2 million Americans have sickle cell trait. Specifically, sickle cell anemia occurs among about 1 out of every 500 African Americans, while sickle cell trait occurs among about 1 out of every 12 African Americans.
Early diagnosis of sickle cell disease is essential for the prevention of Sickle Cell disease complications (such as infections) and for providing life-saving treatment. There is also a need for distinguishing sickle cell anemia from sickle cell trait.
In many circumstances, effective treatment of Sickle Cell disease and its corresponding complications requires rapid diagnosis often outside of the context of a medical facility or hospital. Thus, at the point-of-care, the diagnostic method would be most effective if it could be effectively used and a treatment decision reached by a layperson (i.e., an individual with minimal or no formal medical training or experience). Existing sickle cell screening tests include hemoglobin electrophoresis, genetic testing, high performance liquid chromatography (HPLC), isoelectric focusing, antibody-based assay, and mass spectrometry, all of which are time-consuming and are performed by highly trained health-care professionals in a laboratory setting.
SICKLEDEX™ is a qualitative solubility test used to detect the presence of hemoglobin S; however, the SICKLEDEX™ test cannot distinguish the specific amount, concentration, or percentage of hemoglobin S in a sample. Moreover, SICKLEDEX™ cannot distinguish sickle cell anemia from sickle cell trait.
There has been a long-felt but unmet need for a sickle cell test that can provide point-of-care (POC), rapid, and accurate diagnosis of sickle cell disease. Furthermore, there is a need for a POC sickle cell test that can be easily operated by a user without medical expertise or training (a layperson). As will be clear from the disclosure that follows, the present invention provides solutions to address these needs.